Random Light and Darkness

Recently I have been noticing random brightening and darkening of my vision. Since it has some inclination of light, I decided to add it here. Whenever I am doing something or paying attention to a lecture, everything will become bright and white for a half a second. My whole eyesight will become white. I become fearful that it is just me dreaming or in the verge of dreaming. Another random thing that happens to me is that when paying attention at something, sometimes the edges of my eyesight becomes dark while the center begins to be grayish. It could be that a lot of exposure to light may have caused me to experience these things. Especially since we are being more expose to light as years pass by, because of many people being glued to a screen, the way we see light might be altered by over exposure. Or even the lack of light might make light unbearable if that person was locked in a dark room all the time. Knowing the possibility that what everyone sees might be different, I wonder if they perceive light differently and have a totally different experience than someone else.